Laser and Intense Pulsed Light

What is the difference between the selective photothermal action of laser and IPL?

First of all, we all know that intense pulsed light uses the principle of selective photothermolysis, which can cover multiple target chromophores such as melanin, hemoglobin, and water molecules. Likewise, lasers and IPL are both essentially light, and they can also use this principle to work.

However, the difference between them is that intense pulsed light can act on multiple target chromophores, which is widely used and can treat a variety of symptoms at the same time, while laser acts on one target chromophore, which is faster and deeper in wavelength and has a more specific treatment effect.

Therefore, in order to achieve selective photothermal action, the laser must meet the three conditions of wavelength, pulse width and energy density, which is the only way to hit the target area at high speed and make different cells in the skin tissue absorb the corresponding laser wavelength, so as to achieve the corresponding therapeutic effect.

1.Targeting vascular target chromophores

Hemoglobin, a special protein that transports oxygen in red blood cells, has the main function of transporting O2 and CO2. When the barrier function is damaged, capillaries dilate and rupture, and hemoglobin flows out. The target chromophore of laser is oxygenated hemoglobin and hemoglobin. When targeting blood vessels for photoelectric treatment, it can absorb a large amount of heat to coagulate the hemoglobin in the dilated capillaries, and the capillaries are coagulated and eventually converted into high iron hemoglobin.

There are three absorption peaks of hemoglobin, namely 418nm, 542nm and 577nm, with the lowest valley absorption value in the 694nm band. The pulsed dye laser, a representative laser device for blood vessels, has a high absorption rate for both hemoglobin and oxyhemoglobin at 595nm wavelength, and can reach the deeper part of the blood vessels to treat the presence of red blood or rosacea symptoms on the face.

  1. Targeting the target chromophore of Propionibacterium acnes

Propionibacterium acnes, a Gram-stain-positive anaerobic short bacillus, is the main source of bacteria that trigger acne pimples and other folliculitis symptoms. When abnormal oil production occurs in the sebaceous glands, large amounts of saturated fatty acids break down into free fatty acids, inducing hyperkeratosis and blockage of the follicular sebaceous ducts. This then exacerbates the growth of Propionibacterium acnes, releasing hydrolytic enzymes and a variety of inflammatory mediators that induce and exacerbate local inflammation, leading to acne.

The most representative target chromophore for Propionibacterium acnes is LED red and blue light. LED red and blue light is a low-energy light, mainly from light-emitting diodes, which emits a continuous spectrum with a wavelength of 350-110 nm, and is therefore also known as a cold laser. Propionibacterium acnes will produce photosensitive porphyrins during the metabolic process. When blue light is irradiated to Propionibacterium acnes, it will cause the light activation of endogenous porphyrins to play a bactericidal role. Red light, on the other hand, is mainly anti-inflammatory, improving capillary dilation and accelerating skin repair.

  1. Targeting water molecule target chromophores

Under the principle of photothermal action, the laser can heat the water molecules inside and outside the cells to stimulate collagen regeneration. The absorption coefficient of water starts to rise after the wavelength of 1200nm, and there are peak absorption values at 1500, 1900, 3000 and 6200nm respectively.

Fractional laser has focal characteristics, its beam diameter is less than 500 μm, regularly arranged into fractions, and target the water molecule target chromophores in the tissue, focal photothermal effect to play a therapeutic role, so that its absorption of laser energy into heat, resulting in a very small matrix of thermal damage area, and then stimulate collagen regeneration.

  1. Targeting melanin target chromophores

Most melanin deposits in the skin are caused by the production of melanin by melanocytes located in the basal layer of the skin. Tyrosine meets tyrosinase (TYR) and various oxidase enzymes in melanocytes and undergoes hydroxylation to become DOPA dopa, which is finally oxidized to form dopaquinone to produce brown melanin and true melanin, which are continuously synthesized and increased in melanosomes and released upward from melanocytes to move to stratum corneum.


The absorption value of melanin is between 280-1200nm and decreases with increasing wavelength. The laser device is the most representative laser product for melanin target chromophores. 755nm melanin is particularly accurate with higher absorption value, which can improve the melanin removal rate. 

  1. Targeting fat target chromophores

Laser lipolysis mainly takes advantage of the largely constant number of fat cells in adults to produce radiofrequency waves for non-invasive selective heating of the subcutaneous tissue. When the skin temperature rises, the lipase activity in the body is activated, breaking down triglycerides into free fatty acids, causing the fat cells to decrease in size and accelerating metabolism until they die.

The representative for fat target chromophore has 5G Angel Light Sculpture, which uses 1470nm laser wavelength, at the peak value of water molecules, which is easier to play the thermal effect to destroy fat cells and accelerate fat reduction.

Different laser devices, in terms of clinical indications, can play the proper treatment role for a variety of target chromophores such as blood vessels, water molecules, melanin, fat, and Propionibacterium acnes, thus helping candidates to solve skin problems in a more targeted manner.

With the development of the medical aesthetic industry, various technologies are also being updated and iterated. From the supply side, technological progress lays a solid foundation for the development of the medical beauty industry. Hebei Sunhingtech Co.,Ltd hope to keep communication on the development and progress of new technologies and materials in the industry.



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